Long-term influence of dietary conjugated linoleic acid supplementation on induction of T cell responses to viral or bacterial antigens

Bassaganya-Riera, J., R. Hontecillas, D.R. Zimmerman, and M.J. Wannemuehler (2001) Long-term influence of dietary conjugated linoleic acid supplementation on induction of T cell responses to viral or bacterial antigens. Proceedings of the 82^nd Annual Meeting of the Conference of Research Workers in Animal Diseases; Nov 11-13; St. Louis, MO; (Abstract #130).

Porcine CD8+ lymphocytes are critical for the development of cellular immune responses to bacterial (i.e., CD8αα+) and viral (i.e., CD8αβ+ ) pathogens. Vaccination and challenge modulate the kinetics of appearance of CD8+ cells in peripheral blood. In addition to antigen-mediated immunomodulation, cell-mediated immunity can also be controlled nutritionally. We had previously observed that diets supplemented with a mixture of conjugated linoleic acid (CLA) isomers expanded numbers of porcine CD8+ peripheral blood mononuclear cells (PBMC). The present study aimed to investigate the influence of prior consumption of dietary CLA on phenotype and effector functions of porcine T cells following immunization with a bacterial and/or a viral antigen. Eight groups of two littermate pigs were fed either a CLA-supplemented diet or an isocaloric diet supplemented with soybean oil. After 72 days of a dietary supplementation with the two experimental diets, pigs were provided a nutritionally-appropriate, unsupplemented diet for 75 additional days. On days 0, 20, and 50 post-withdrawal of dietary CLA, pigs were inoculated with squalene adjuvant preparation alone, proteinase-digested B. hyodysenteriae B204, modified-live pseudorabies, or both vaccine preparations. Flow cytometric evaluation of PBMC revealed that the effects of dietary CLA on immune cell phenotype (i.e., numbers of CD8αβ+ cells) persisted 67 days after the compound was withdrawn from the diet. However, diet-mediated regulation of effector functions (i.e., antigen-stimulated proliferation and cytotoxycity) disappeared earlier (i.e., 25 days) as shown by proliferation and granzyme activity assays. Specifically, numbers of CD8αβ+ PBMC in pigs that had been fed diets supplemented with CLA were greater than in pigs fed control diets, regardless of the vaccination treatment. Furthermore, prior dietary CLA supplementation interacted with viral immunization (i.e., modified-live pseudorabies virus vaccine) by enhancing both pseudorabies-specific proliferative responses of CD8αβ+ lymphocytes and granzyme activities of PBMC.